This invention relates to new and useful improvements in internal combustion engines, particularly to the efficiency of the conventional air/fuel mixture which is normally in the neighborhood of 12 to 16 to 1 by volume.
Even under optimum operating conditions, it is usually not possible to operate at more than 25 to 28 percent efficiency, the remaining power being lost due to friction, heat, and general inefficient burning conditions. The heat losses are absorbed by the cooling system and inefficient burning is absorbed in the exhaust system and discharged into the atmosphere with the subsequent pollution problems.
It has long been recognized that if only a small increase in percentage efficiency could be obtained, then fuel economy would be improved and exhaust emissions also would be improved. Prior art devices have attempted to improve the operating conditions and included U.S. Pat. No. 2,091,413 in which a rich mixture is injected under comparatively high pressure into a cylinder containing air. U.S. Pat. No. 2,154,856 shows a pair of cylinders which are in constant communication with each other through a common combustion chamber and the pistons are connected to a common crank shaft but are so arranged that one piston leads the other. This of course intends to provide an unbalanced engine.
U.S. Pat. No. 3,866,582 shows pairs of cylinders operating together with a common exhaust valve and constant communication between the two cylinders. U.S. Pat. No. 3,200,799 operates on a modified Atkinson cycle characterized in that the expansion ratio exceeds the compression ratio. It teaches the use of a pair of cylinders in which a charge is induced and partially compressed in one cylinder but finally compressed in the two cylinders into a common combustion chamber. U.S. Pat. No. 2,196,228 shows a pair of cylinders but the pistons move in different directions and one piston is larger than the other and finally U.S. Pat. No. 2,255,925 relates to a two stroke multi-stage engine which includes first and second stages with a small charge and with a running as is the case in a two-stroke single stage internal combustion engine of usual construction.
The present invention overcomes the above mentioned disadvantages and disadvantages inherent in the prior art devices and in accordance with the invention there is provided an internal combustion engine operating on the Otto cycle and including intake, compression, expansion and exhaust strokes. It comprises at least one pair of piston and cylinder assemblies which includes combustion chambers and cylinder heads in side by side relationship and which constitute a master piston and cylinder assembly and a secondary piston and cylinder assembly. An inlet and an exhaust valve is provided in the master piston and cylinder assembly and at least an exhaust valve is provided in the secondary piston and cylinder assembly. Means are provided whereby the pistons of the master and secondary piston and cylinder assemblies reciprocate in side by side relationship concurrently and a transfer valve assembly extends between the combustion chambers of the master and secondary piston and cylinder assemblies. The transfer valve assembly is situated in the combustion chamber of the master piston and cylinder assembly and adjustable means normally maintain the transfer valve assembly closed below a predetermined pressure within the master combustion chamber which is in excess of the compression pressure generated therein.
Another aspect of the invention contemplates the provision of an inlet valve in the secondary piston and cylinder assemblies which may be operated to introduce either a limited charge of air/fuel mixture of approximately the same ratio as the conventional air/fuel ratio or, alternatively, may introduce a charge of air/fuel mixture which is much leaner than normal and which normally would not ignite under normal compression ratios utilized. However, because of the transfer valve assembly being opened at this time, the high temperatures of the burning air/fuel mixture within the master piston and cylinder assembly is sufficient to ignite the lean mixture in the secondary piston and cylinder assembly once again adding to the efficiency of the operation of the engine.
Still another aspect of the invention is to provide a device of the character herewithin described which can be incorporated in an existing engine with the minimum of modification being required.
With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention, in which: